Cefaclor, cephalexin, cephradine and loracarbef have the structures as set out below: ##STR3## The four .beta.-lactam compounds, in which the C-2' (*) asymmetric centers have the R absolute configuration, are commercially important oral antibiotics.
Various references discuss isolation and/or purification processes for the .beta.-lactam compounds, such as that found in European Patent Application 0,341,991 published Nov. 15, 1989. In that EPO application is disclosed the use of anthraquinone-1,5-disulfonic acid to form a pharmaceutically acceptable salt with the particular cephalosporin or carbacephalosporin, which allows for recovery of the .beta.-lactam from mother liquors after crystallization.
As these antibiotics are expensive to make, new and improved procedures for such recovery are continually being sought in order to maximize overall yield.